GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Transcription Proteins

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #1 : Help With Transcription Proteins

In eukaryotes, which RNA polymerase makes rRNA?

Possible Answers:

RNA polymerase II

RNA polymerase IV

RNA polymerase III

RNA polymerase I

Correct answer:

RNA polymerase I

Explanation:

The RNA polymerases are numbered in the order that their products are used in protein synthesis.

RNA polymerase I makes ribosomal rRNA in eukaryotes.

RNA polymerase II makes messenger mRNA in eukaryotes.

RNA polymerase III makes transfer tRNA in eukaryotes.

Example Question #2 : Rna, Transcription, And Translation

Which of the following subunits of RNA polymerase is solely required for initiation of transcription?

Possible Answers:

 (omega)

 (beta)

 (sigma)

 (alpha)

Correct answer:

 (sigma)

Explanation:

The sigma factor is solely required for the initiation of transcription. In fact, the sigma subunit will often fall off of the enzyme during the elongation phase of transcription. Binding of the sigma factor is an important signal for transcription to begin.

The other subunits are crucial to the elongation and termination phases.

Example Question #2 : Help With Transcription Proteins

Which of the following codons is the mRNA start codon that initiates translation?

Possible Answers:

UAG

AUG

UGA

UAA

Correct answer:

AUG

Explanation:

The codon AUG initiates translation in both eukaryotes and prokaryotes. Interaction with this codon by a tRNA molecule allows a methionine residue to enter the ribosome and serve as the starting point for amino acid elongation.

UGA, UAA, and UAG are mRNA stop codons and stop protein synthesis by causing the ribosomal subunits to dissociate and release the polypeptide.

Example Question #3 : Transcription And Rna

Which of the following best describes the key function of helicases during transcription?

Possible Answers:

Cleaving methyl groups from an unwound DNA strand. 

Separation of two strands of DNA; "unwinding" gives polymerases access to the strand. 

Catalyzing the interaction between transcription factors and the DNA strand. 

Relief of tension in the DNA strands to prevent breakage. 

Re-annealing of two DNA strands once transcription and translation processes are complete.

Correct answer:

Separation of two strands of DNA; "unwinding" gives polymerases access to the strand. 

Explanation:

Helicases are required for separating two DNA strands so that the rest of transcription can take place. Polymerases work on single strands of DNA, thus the bonds holding the double strands together must be removed. 

Example Question #4 : Transcription And Rna

Transcription factors that are the first to bind DNA in heterochromatin regions, often promote euchromatin formation, and recruit other transcriptional machinery to promote transcription are best known as which of the following?

Possible Answers:

Histone demethyltransferases

Co-factors

DNA Polymerases 

RNA holoenzyme 

Pioneer factors

Correct answer:

Pioneer factors

Explanation:

The correct answer is pioneer factors. Pioneer factors are able to bind DNA in condensed regions and promote euchromatin formation by recruitment of histone demethyltransferases and acteyltransfereses to modify proximal histones. Additionally, these pioneer factors recruit other transcription factors and co-factors to promote transcription. DNA polymerases are involved with DNA replication, not transcription. The RNA holoenzyme is a protein complex consisting of RNA polymerase, transcription factors, and regulator proteins that binds promoters and catalyzes transcription. 

Example Question #6 : Rna, Transcription, And Translation

Before RNA polymerase can initiate transcription, this protein must bind to it, creating the RNA polymerase holoenzyme and allowing for the initiation of transcription.

Possible Answers:

Sigma factor

Topoisomerase

Helicase

Beta factor

Activator protein

Correct answer:

Sigma factor

Explanation:

RNA polymerase cannot initiate transcription by itself. It binds to the promoter but must wait for a sigma factor to bind to it. Now the RNA polymerase holoenzyme can proceed with transcription.

Example Question #7 : Rna, Transcription, And Translation

Which of the following is not dependent on the C-terminal domain (CTD) of RNA polymerase II? 

Possible Answers:

mRNA splicing

None of the other answers 

5' capping 

Polyadenylation 

Transcription termination 

Correct answer:

None of the other answers 

Explanation:

The correct answer is none of the other answers. Only mRNA transcribed by polymerase II undergo 5' capping, polyadenylation, and splicing. The C-terminal domain of this polymerase serves as a binding site and docking platform for many of the enzymes that initiate these processes. Moreover, experiments in which the CTD is truncated show that mRNA transcripts are not capped, polyadenylated, and spliced. 

Example Question #8 : Rna, Transcription, And Translation

Which polymerase is involved in transcribing ribosomal RNA (except 5S rRNA)?

Possible Answers:

RNA polymerase I

DNA polymerase IV

RNA polymerase II

RNA polymerase III

DNA polymerase V 

Correct answer:

RNA polymerase I

Explanation:

The correct answer is RNA polymerase I. The sole purpose of RNA polymerase I in eukaryotes is to transcribe ribosomal RNA, with the exception of 5S rRNA, which is transcribed by RNA polymerase III. RNA polymerase III also transcribes tRNAs and other small RNAs. Transcripts of RNA polymerase II are 5' capped, polyadenylated, and spliced to ultimately be translated into functional protein. DNA polymerase IV/V are polymerases involved in DNA replication and repair. 

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
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